Malcolm Turnbull told the partyroom on Tuesday that nobody was more committed to “embracing our broad church” – the liberal and conservative traditions of the Liberal Party – than he was.

That’s code for reassuring the party’s conservatives that they can trust him – which of course many do not.

The Nationals form a separate church, but one whose members have long memories, all the way back to the time when they had big issues with then-opposition leader Turnbull over climate policy and the like.

In search of conservative votes for the leadership, Turnbull quite a while ago made it clear he would not change the government’s policy on emissions reduction. No flirting with an emissions trading scheme. More recently, he has also embraced the Abbott policy for a popular vote on same-sex marriage next term.

It’s not so hard for him to explain away the shift on climate policy – his attacks on Direct Action were years old; as a minister he has had to support the policy, and things have moved on.

Same-sex marriage is more awkward. Turnbull was a strong advocate for having parliament to decide that on a free vote. When he and others lost that argument a few weeks ago and Abbott declared the people should decide, Turnbull said he would prefer a plebiscite to be held before the election, so the issue would not be a distraction.

But pressed by the opposition in parliament on Tuesday, it was a different story. Turnbull sounded to be channelling Abbott. “There is no greater virtue in a free vote here [in parliament] or a plebiscite,” he said. “They are each means of resolving the matter – one, I grant you is more expensive but, nonetheless, it is a very legitimate and democratic way of dealing with it.

"At the next election, Australians will have a choice. The Labor Party will say vote for us and marriage equality will be dealt with by the politicians in a free vote after the election. And we will say, if we are re-elected to government, every single Australian will have a say.”

Unlike his predecessor Turnbull strongly believes in same-sex marriage, and supporters of change can have more faith that the promise of a plebiscite would be carried through under him. But the vote would be still a long way off.

There is no doubt that Turnbull’s compromises helped him to round up numbers for Monday’s win. But some people, especially the more progressive Liberals, will be disillusioned when they see Turnbull ditch former positions on issues when he had made so much of them. From his perspective, however, those people are on side – it is the conservative end of the party he was and is trying to bind in.

The Nationals have taken the precaution of getting undertakings from Turnbull in writing, with their leader Warren Truss frankly admitting past differences. Truss said this was the first time that the normal Coalition agreement – covering the proportion of frontbench jobs – was accompanied by a letter outlining policy commitments.

These cover a range of areas including climate policy and same-sex marriage.

One of the more controversial provisions is for water policy, including responsibility for the Murray Darling Basin Authority, to go from the Environment Minister Greg Hunt to Agriculture Minister Barnaby Joyce – that is, from the Liberals to the Nationals. This won’t please environmentalists, or some in South Australia concerned about the lower Murray.

Hunt’s response, incidentally, is to say his work on water reform has been largely completed.

A potentially troublesome undertaking is for cabinet to give “proper consideration” to amendments to the Australian Competition and Consumer Act “to prevent abuse of market power”. This is the “effects test” – a proposal put up by Small Business Minister Bruce Billson that would strengthen the hand of small businesses against large companies.

It has been a touchy and divisive matter within the government. Three Nationals crossed the floor on a Senate motion from the Greens about it on Tuesday. Big business has been particularly critical of the proposal. It won’t be impressed if Turnbull supports the test in cabinet because of his deal with the Nationals. And the Nationals will be very critical of him if he doesn’t give it his backing.

When Turnbull takes up a position or runs a line he puts it with all the passion of a conviction politician. But his compromises show an approach that is more driven by pragmatism – which can be a good thing or a bad thing, depending on the circumstances.

If, for example, he were to put Christopher Pyne into the defence portfolio – it’s been a rumour – with an eye to a particular outcome on submarines and South Australian seats, that would be an alarming sign from the new prime minister.